High speed downlink packet access (HSDPA) is wideband code division multiple access (WCDMA) key feature which provides high data rate transmission in a CDMA downlink to support multimedia services. Downlink data transmission is provided by a high speed physical shared control channel for HS-DSCH (HS-SCCH) and a high speed physical downlink shared channel (HS-DSCH) associated to the control channel. The control channel provides a terminal with information that data for the terminal is arriving on the data channel.
Prior to data transmission on the data channel, the prior art introduces no power control mechanism for the control channel. Only when data transmission has started, power of the control channel can be adjusted by applying either an open or a closed power control mechanism.
One of the disadvantages in the prior art is that the initial power level applied for the HS-SCCH is not optimal in view of interference in the network. The network may apply for a new user a safe average power level, which may be unnecessarily high. The uncertainty of the power level for the HS-SCCH may also imply a too high power level for a corresponding uplink control channel, that is high speed dedicated physical control channel HS-DPCCH associated with a HS-DSCH transmission in DL. The disclosed problem applies in prior art to the uplink transmission as well, and there is no power control mechanism for a control channel before data transmission on an associated data channel. The prior art also has the problem that the outer loop of the power control is slow. The problem is that the BLER (Block Error Rate) target of the HS-SCCH is small; hence very little errors occur that can be used in the power control. When the HS-PDSCH is transmitted, one cannot increase the errors on HS-SCCH, as they would automatically cause the data transmission to be unnecessary.